In recent years, the display device has advanced in slimming down, and a display device called a FPD (flat panel display) has become widely used. The FPD is classified based on the light emission principle, and studies on various FPDs are being carried out, such as an electro luminescence display, a plasma display, etc.
In particular, the liquid crystal display device has a high penetration ratio compared with other types of display devices, and attracts attention, and the demand for display characteristics (image quality) is particularly strong.
Meanwhile, in the display device, when displaying an image captured by an image capture device such as a camera or a scanner, there is a case that color information is not accurately reflected. That is, there is a case that deviation is caused in color expression between the image capture device and the display device.
This is often caused by that the standard defining color expression differs between the display device and the image capture device. That is, when a color that is defined on one hand is not defined on the other hand or a color that can be expressed on one hand is not in the range that can be expressed on the other hand, color expression deviation is caused.
Regarding this issue, as a standard color space for the computer display, the sRDB standard was established as an international standard (IEC61966-2-1) in October of 1999. This sRGB standard was established for the purpose of standardizing color reproducibility and color space that have been notably different manufactures by manufactures and devices and devices.
By standardizing color reproducibility between televisions, digital still cameras, and printers and mobile devices, it becomes possible to match the image color information expressed by mobile devices and the image color information expressed by input/output devices. The sRGB standard clearly defines the relationship between video signals RGB and colorimetry values by matching the chromaticity points of three primary colors (RGB) to the colorimetry parameters of Rec. 709 recommended by ITU.
As the characteristics (elements constituting image quality) demanded for display devices, color reproducibility can be given. As the color reproducibility is broader, versatile color expressions become possible, so that color reproducibility is important. However, as the color reproducibility expands, the center wavelength of an emission spectrum of each color (for example, red, green, blue) tends to depart from the wavelength (555 nm) that is high in the distinct vision sensitivity for human beings, and the spectrum width tends to become narrower, so that the luminance decreases. That is, color reproducibility and luminance are in a so-called trade-off relationship.
To constitute a display device meeting the above-described sRGB standard, in this trade-off relationship, the color reproducibility must be pursued while avoiding extremely damaging the luminance.
However, the color reproducibility of display devices is insufficient, and the color expression meeting the above-described sRGB standard has not been accomplished.
For example, in a display device employing a method of illuminating a liquid crystal using a light source device separately provided, a so-called white LED has been known as the light source device, in which fluorescent bodies each bearing emission of at least one color and a light-emitting body (light emitting diode) bearing emission of a wavelength shorter than the emission wavelength band of these fluorescent bodies are combined. However, in the configuration that has been regarded as the mainstream in the past, in which YAG:Ce is used for the fluorescent body bearing emission of yellow (yellow fluorescent body), the emission spectrum of the fluorescent body spreads in a broad range from the green gamut to the red gamut.
Because of this, if the light from this fluorescent body is caused to pass a color filter, the emission spectrum of another color comes to be mixed a lot in the green color filter and the red color filter, and pure green color and red color cannot be developed.
Further, a proposal has been made to try to increase the chromaticity points that can be expressed, using a green fluorescent body and a red fluorescent body (for example, see Patent Document 1).
However, even if the color reproducibility is blindly improved, luminance decrease is accompanied, so that this has the opposite effect that the quality of the display device decreases. That is, it is desirable to try to accomplish improvement in the color reproducibility by selectively enabling color expressions that are required by the sRGB standard.
The chromaticity point of red color in the sRGB standard is (0.640, 0.330), and it is regarded difficult to express this chromaticity point. The measured chromaticity point of red color of a currently commercially available display device for mobile use was (0.632, 0.351). The display device measured is a product called a wide color gamut mobile display, however, because the fluorescent body used in the white LED is a yellow fluorescent body, it is believed that the color expression for red is insufficient.
Red plays a particularly important role in the color reproducibility, as the eye-catching color (the color high in the eye-catching property in color engineering), separately from the distinct vision sensitivity, however, it is regarded as difficult to constitute a display device that can express red color of the sRGB standard.    [Patent Document] Japanese Unexamined Patent Application Publication No. 2004-163902